Editor's note: This article was excerpted from our Import/Export Business start-up guide, available from the Entrepreneur Bookstore.International trade is one of the hot industries of the new millennium. But it's not new. Think Marco Polo. Think the great caravans of the biblical age with their cargoes of silks and spices. Think even further back to prehistoric man trading shells and salt with distant tribes. Trade exists because one group or country has a supply of some commodity or merchandise...